The present invention is related to a pointing position correcting method, a pointing position correcting apparatus, and a pointing apparatus, which correct a shift between a pointing position when a rotation of a pointer is stopped by that a driven member rotated in conjunction with a rotation of this pointer abuts against a fixed stopper, and a reference pointing position for pointing a zero on a scale, while the pointer is rotated by a stepper motor in such a manner that this pointer points a place in response to a measurement amount on a scale.
Conventionally, as a pointing apparatus for pointing out a place of a scale responding to a measurement value on a dial by rotating a pointer by a stepper motor, for instance, such a pointing apparatus is known which contains pointers for pointing out a speed of a vehicle and an engine revolution number. As represented in FIG. 12, the above-described pointing apparatus is equipped with a stepper motor 19 having two energizing coils 19a and 19b and a magnet rotor 19c; a pointer 17; gear trains 21 and 23; and a driving control apparatus 41. In the magnet rotor 19c, N and S poles are alternately magnetized in a multiple polarity mode, and the magnet rotor 19c is rotated in response to changes in energizing conditions of the energizing coils 19a and 19b. The pointer 17 is rotated in conjunction with rotation drives of the magnet rotor 19c. The gear trains 21 and 23 transfer the rotation drive force of the magnet rotor 19c to a pointer 17. The driving control apparatus 41 controls the energizing conditions of the energizing coils 19a and 19b so as to rotate the magnet rotor 19c along a normal direction and a reverse direction.
In the case that the above-described pointing apparatus is employed as a vehicle speed indicator (vehicle speedmeter), angle data “D1” indicative of a rotation angle of the magnet rotor 19c is supplied to the driving control apparatus 41. This angle data D1 corresponds to a move amount “?=?′” which is equal to a difference between a target position “?” and a present position “?′.” The target position “?” is equal to such a position on a scale, which should be pointed out by the pointer 17 and has been calculated based upon vehicle speed information measured by a vehicle speed sensor. The present position “?′” is equal to such a position on the scale, which is presently pointed out by the pointer 17. Then, the driving control apparatus 41 controls the energizing conditions of the energizing coils 19a and 19b in response to this angle data D1, so that the pointer 17 is moved by the difference “?−?′” so as to point out the target position.
On the other hand, since the angle data D1 is inputted to which either vibrations of the vehicle or noise has been superimposed, a loss of synchronism may occur in which the move amount (=difference “?−?′”) over which the pointer 17 must be originally moved is different from the actual move amount. Then, if this loss of synchronism repeatedly occurs, then there is a difference between the speed (namely, position on scale) which is actually pointed by the pointer 17 and the speed (namely, position on scale) which should be originally pointed by the pointer 17 and corresponds to the speed information measured by the speed sensor. As a result, the pointing apparatus cannot point out the correct speed.
To solve such a problem, as indicated in FIG. 13, a stopper 31 is provided on a dial 43 in such a manner that when the pointer 17 points out 0 Km/h on the scale of the dial 43, the pointer 17 abuts against this stopper 31. Every time an ignition switch is turned ON/OFF, or a battery is connected, such a reset operation has been carried out (for example, patent publication 1). That is, in this reset operation, since the pointer 17 is moved to the side of the stopper 31 and also is forcibly stopped at the zero position where the pointer 17 points out 0 Km/h on the scale, a difference between a speed pointed by the pointer 17 and speed information measured by the speed sensor is reset.
However, as explained above, when the stopper 31 is provided on the dial 43 of the pointing device, the appearance of the pointing apparatus may be damaged. As a consequence, as represented in FIG. 12, a pin 23a is provided with a gear 23 within the gear trains 21 and 23 located at a rear side of the dial (not shown), while the pin 23a is rotated in conjunction with the gear 23. The stopper 31 which mechanically stops the pin 23a is provided within a housing of a meter in order that the pointer 17 points out 0 Km/h on the dial at such a position that the pin 23a abuts against the stopper 31. If such a construction is employed, then the stopper 31 does not appear on the front surface thereof, but also the appearance of the pointing apparatus is not damaged (for example, patent publication 2).
On the other hand, generally speaking, in a meter using this sort of pointer 17, such a work for driving the pointer 17 in a pointer shaft (not shown) is required, while this pointer shaft penetrates a center of a magnet rotor 19c of a stepper motor 19. In this driving work, the position where the pointer 17 is driven with respect to the pointer shaft is positionally shifted from the original point along the rotation direction of the pointer shaft.
Then, in the case that the pointer 17 is driven in the pointer shaft while this pointer 17 is actually shifted along the rotation direction of the pointer shaft, as to the pointing apparatus in which the stopper 31 is provided on the dial 7 as previously explained with reference to FIG. 13, when the pointer 17 abuts against the stopper 31, the pointing position of the pointer 17 with respect to the scale on the dial 7 is reformed to the zero position where the pointer 17 points out 0 Km/h on the scale irrespective of such a condition as to whether or not there is a shift in the position where the pointer 17 is driven with respect to the pointer shaft. In this case, if the reset operation is carried out, then the difference between the speed pointed out by the pointer 17 and the speed information measured by the speed sensor is reset without trouble.
However, as shown in FIG. 12, in the pointing apparatus for providing the pin 23a on the gear 23 provided on the rear side of the dial, if the driving position of the pointer 17 is shifted along the rotation direction of the pointer shaft, then the position of the pointer 17 with respect to the pin 23a provided on the gear 23 is shifted along the rotation direction of the pointer shaft. As a result, even when the pin 23a abuts against the stopper 31, the pointer 17 does not point out 0 Km/h on the dial, but may point out such a position which is shifted by a driving shift of the pointer 17. As a consequence, there is a deviation between a speed pointed by the pointer 17 and speed information measured by the speed sensor, so that the pointer 17 cannot point out the correct speed.
Therefore, the Applicant has proposed the pointing apparatus in the past. That is, in such a pointing apparatus in which the pin 23a is provided on the gear 23 located on the rear side of the dial as shown in FIG. 12, even when the pointer 17 is mounted on the pointer shaft with a shift while maintaining such a positional relationship that when the pin 23a abuts against the stopper 31, the pointer 17 points out a place other than 0 Km/h on the dial, such a reset operation is carried out in order that the pin 23a abuts against the stopper 31. Thereafter, the shift of the mounting position of the pointer 17 with respect to the pointing shaft thereof can be reformed, and thus, the pointing position of the pointer 17 can be corrected to such a position that the pointer 17 points out 0 Km/h on the scale.
However, if the pointer 17 is driven with a shift with respect to the pointer shaft in such a manner that when the pin 23a abuts against the stopper 31, the pointer 17 points out such a place which is shifted to a plus direction (direction along which pointed value on scale is increased: right turning direction in FIG. 12) from 0 Km/h, then it is physically impossible to rotate the pointer 17 along a minus direction (direction along which pointed value on scale is decreased: left turning direction) and to reform the shift as long as the pin 23a abuts against the stopper 31.
Thus, in the pointing position correcting apparatus which has been proposed in the past by the Applicant and a pointing apparatus containing this pointing position correcting apparatus, while the maximum shift amount of the pointer 17 with respect to the pointer shaft is previously predicted, even when the pointer 17 is driven with respect to the pointer shaft with being shifted by this maximum shift amount, the relative position between the stopper 31 and the pin 23a is set in such a manner that when the pin 23a abuts against the stopper 31 by way of the reset operation, the pointer 17 points out such a place which is slightly shifted from 0 Km/h on the dial along the minus direction.
Then, after the reset operation has been carried out, the correcting operation is performed (patent publication 2). In this reset operation, while the rotation amount of the magnet rotor 19c has been written in the memory and this rotation amount is required so as to return the zero scale on the dial to the position pointed by the pointer 17, the pointer 17 is rotated along the minus direction until the pin 23a abuts against the stopper 31 under control of the driving control apparatus 45. In the correcting operation, the magnet rotor 19c is rotated by the rotation amount written in the memory so as to rotate the pointer 17 along the plus direct, so that the pointer 17 is returned to such a position for pointing out the zero scale on the dial.
Patent publication 1:
Japanese Laid-open Patent Application No. 2002-5698
Patent publication 2:
Japanese Laid-open Patent Application No. 2002-139354
On the other hand, in a general-purpose combination meter having plural sets of the pointers 17 (for example, speed meter, tachometer, fuel meter, water temperature meter etc.) which are rotated by the stepper motor 19, there are some possibilities that the above-described problem may occur as to each of these plural meters. That is, the driving position of the pointer 17 with respect to the pointer shaft after the gear 23 has been mounted is shifted along the rotation direction of the pointer shaft with respect to the position of the pin 23a provided on the gear 23. Moreover, there are great possibilities that shift amounts produced in the respective meters are fluctuated.
As a result, in the pointing apparatus with employment of the rotation amount of the pointer 17 along the minus direction during the reset operations, which has been uniformly set, the rotation amounts (time durations) required until the pins 23a abut against the stoppers 31 are fluctuated between a meter having a large shift amount as to a driving position of the pointer 17 with respect to the pointer shaft, and another meter having a small shift amount as to a driving position of the pointer 17 with respect to the pointer shaft. Thus, even after the pin 23a has already abutted against the stopper 31 in the meter having the small shift amount of the driving position of the pointer 17, the control operation cannot be advanced to the next correcting operation and therefore is under waiting condition until the pin 23a abuts against the stopper 31 in the meter having the large shift amount of the driving position of the pointer 17.
As previously explained, in the combination meter having a plurality of such pointers 17 rotated by the stepper motors 19, as the stopper construction of each of these meters, when such a construction shown in FIG. 12 is employed, in the case that both the reset operations and the correcting operations are necessarily carried out, anew technical idea is necessarily required in order that the pointers 17 of the respective meters are more quickly advanced to the normal operations as to a different point from such a case that both a reset operation and a correcting operation are carried out with respect to a single pointer 17. In the above-explained stopper construction, the pin 23a is provided with the gear 23 located on the rear side of the dial, and this pin 23a abuts against the stopper 31 provided in the housing.